Single-conductor transformer for high-voltage installations

ABSTRACT

A single-conductor transformer for installation in the metal encapsulation of a fluid-insulated, high-voltage installation has at least one iron core with a secondary winding system mounted thereon. The iron core with its secondary winding system is disposed within a cylindrical, grounded metallic shield with rounded end-faces and the transformer is arranged inside the metal encapsulation. The metallic shield can be made up of a metal tube which is connected at its one end by means of a fastening shoulder with a fastening projection at the metal encapsulation and at its other end, by means of a further fastening shoulder to a support element which is supported at the metal encapsulation. The iron core with a secondary winding system mounted thereon is supported by the metal tube.

A United States Patent [191 Schiemann SINGLE-CONDUCTOR TRANSFORMER FOR HIGH-VOLTAGE INSTALLATIONS [75] Inventor: Heinz Schiemann, Berlin, Germany [73] Assignee: Siemens Aktiengesellschaft, Munich,

Germany [22] Filed: May 17, 1974 21 Appl. No.: 470,903

[30] Foreign Application Priority Data May 17, 1973 Germany 2325450 [52] US. Cl. 336/84; 336/92; 336/174; 336/175 [51] Int. Cl. HOlF 15/04 [58] Field of Search 336/173, 174, 175, 84, 336/82, 90, 92

[56] References Cited UNITED STATES PATENTS 2,214,915 9/1940 Wehrlin 336/174 X 2,701,335 2/1955 Sargeant et a1. 336/174 X 2,862,194 11/1958 Coggeshall et a1 336/174 X 3,380,009 4/1968 Miller 336/174 X 3,456,222 7/1969 Berg 336/174 X 3,525,908 8/1970 Al1mendinger.. 336/174 X 3,629,759 12/1971 Douglas 336/82 11 3,921,113 [451 Nov. 18, 1975 3,835,429 9/1974 Hermstein et a1. 336/174 X FOREIGN PATENTS OR APPLICATIONS 612,070 4/1935 Germany 336/174 243,057 9/1969 U.S.S.R 336/174 773,256 12/1967 Canada Primary Examiner-Thomas J. Kozma Attorney, Agent, or Firm-Kenyon & Kenyon Reilly Carr & Chapin [57] ABSTRACT A single-conductor transformer for installation in the metal encapsulation of a fluid-insulated, high-voltage installation has at least one iron core with a secondary winding system mounted thereon. The iron core with its secondary winding system is disposed within a cylindrical, grounded metallic shield with rounded endfaces and the transformer is arranged inside the metal encapsulation. The metallic shield can be made up of a metal tube which is connected at its one end by means of a fastening shoulder with a fastening projection at the metal encapsulation and at its other end, by means of a further fastening shoulder to a support element which is supported at the metal encapsulation.

The iron core with a secondary winding system mounted thereon is supported by the metal tube.

10 Claims, 2 Drawing Figures US. Patent Noy. 18,1975 3,921,113

Fig.2

SINGLE-CONDUCTOR TRANSFORMER FOR HIGH-VOLTAGE INSTALLATIONS BACKGROUND OF THE INVENTION The invention concerns a single-conductor transformer for installation in a cylindrical part of a metal encapsulation of a gas-insulated or liquid-insulated high-voltage installation. The transformer has at least one iron core with a secondary winding system mounted thereon which is disposed within a cylindrical, grounded metallic shield with rounded end-faces inside the metal encapsulation.

A single-conductor transformer of this kind is described in Deutsche Offenlegungsschrift 1,807,996. In this known single-conductor transformer, the metallic shield consists of a semi-conducting layer which is applied on an enclosure of electrically insulating material which surrounds cores and secondary windings of the known transformers on all sides. The enclosure of the known transformer is rounded in its end-face regions to form an equipotential surface of the electric field.

SUMMARY OF THE INVENTION It is an object of the invention to provide an improved transformer of the kind discussed above. It is a further object of the invention to'provide such a transformer wherein the iron cores with the secondary winding system mounted thereon are not subjected to mechanical stresses due to the shrinkage pressure of an enclosure which could lead to a change in the transmission characteristics of the current transformer.

These objects are realized in the single-conductor transformer according to the invention with the feature of a metal shielding tube which is connected at its one end by means of a fastening shoulder with a fastening projection at the metal encapsulation and at its other end, by means of a further fastening shoulder with at least one support element which is supported at the metal encapsulation. The transformer includes at least one iron core with a secondary winding system mounted thereon which is carried by the metal tube.

The primary advantage of the single-conductor transformer according to the invention is that no mechanical stresses are exerted on the iron cores because of the absence of an enclosure for the cores and the secondary windings so that permeability changes and therefore, current error changes are avoided. Such an enclosure is usually made of cast resin. A further advantage is seen in the fact that because of the attachment of the iron cores at the metal tube, the transformers are accessible at any time because of the absence of an enclosure and it is therefore possible to adjust turns even during the installation of the single-conductor transformer in the high-voltage installation.

According to another feature of the single-conductor transformer, the iron core can preferably be attached at the metal tube by means of a mounting element. The mounting element can be configured as a single ring or may also consist of several rod-like elements which are preferably attached uniformly distributed over the circumference of the iron cores,

The mounting element of the iron cores can be attached at the metal tube by welding; or, the mounting elements can be bolted to the metal tube. However, in this latter instance, it is essential that at no point there exist weak insulation in the interior of the metal tube due to a screw connection. The iron cores can also be 2 cemented to the metal tube with the interposition of in sulating pieces.

The iron core can also be held advantageously to the metal tube by a clamping arrangement. Here, the clamping arrangement need not consist only of pressure screws, but a clamping device may also be used which is equipped with wedge-like elements instead of pressure screws.

The metal tube of the single-conductor transformer according to the invention can be configured in different ways. It may, for instance, consist of a single metal tube which is enlarged at both ends so as to form rounded end-faces. Such a metal tube, however, will usually be used only if cut tape-cores are used as the iron cores for the single-conductor according to the invention.

If, however, uncut tape cores are to be used, then the metal tube is advantageously composed of several parts.

The metal tube can preferablyconsist ofa center section with two outer parts having rounded end-surfaces. In a metal tube configured in'this manner, the fastening shoulders at the center section and the fastening tabs at the outer parts are clamped, for manufacturingreasons, together with-the support element or the connect ing member, respectively, the connecting member being attached at the fastening projection of the metal encapsulation. The support element as well as the connecting member can be made as a washer; but it is also possible to make these parts of individual elements which are distributed over the circumference of the metal tube preferably uniformly. The same applies to the fastening shoulders and the fastening projections.

Although the invention is illustrated and described herein as a single-conductor transformer for high-voltage installations, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein within the scope and the range of the claims. The invention, however, together with additional objects and advantages will be best understood from the following description and in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram, partially in section, showing the single-conductor transformer according to the invention mounted in the metal encapsulation of a high-voltage installation.

FIG. 2 is a schematic diagram, also partially in section, illustrating an alternate embodiment of the singleconductor transformer according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Referring to FIG. 1, a high-voltage conductor 3 is arranged in an encapsulating metal enclosure 1, of which a section is shown, of a high-voltage switching installation 2. The high-voltage conductor 3 is surrounded by a metal tube 4, which consists of a tube part 5 with a rounded end-face 6 and a further tube part 7 with a rounded end-face 8; both tube parts 5 and 7 are connected with each other by a welded seam 9.

At its rounded end-face 6, the metal tube 4 has a fastening shoulder 10, and at its rounded end-face 8 a further fastening shoulder 11. The fastening shoulder 10 is connected, for instance, by several screws to a fastening projection 12 of metal, which is welded to the metal enclosure 1. A support element 13 of insulating material, which rests againstthe metal encapsulation 1, is bolted to the further fastening shoulder 11; The holes provided in the fastening shoulderslO and 11 and in the fastening projection 12 and the support element 13, respectively,- for receiving the screws are made advantageously larger than the shank diameter of these screws to make centering of the metal tube 4 during the installation into the metal enclosure 1 possible. The metal tube 4 is metallically connected with the metal enclosure 1 via the fastening shoulder and the fastening projection 12 and is thereby grounded.

The single-conductor transformer shown in FIG. 1 contains two iron cores 14 and 15, each of which support aisecondary winding system 14 and 15. At each iron core 14, 15, a holding element 18, 19 is arranged which is fastened to the metal tube 4 by means of a welded joint. The secondary leads 20 and 21 of the secondary winding systems 16 and 17 are brought out of the metal enclosure 1 in a manner not shown.

In the embodiment shown in FIG. 2 of the singleconductor transformer according to the invention, a highvoltage conductor 32 is again arranged in an encapsulating metal enclosure of a high-voltage switching installation 31. The high-voltage conductor 32 is surrounded by a metal tube 33 consisting of a center tube part 34 andan outer part 35 as well as a further outer part 3'6. While the center :tube part 34 is of circular cross -seetion throughout, the outer parts 35 and 36 are provided withrounded end-faces 37 and 38. The outer parts 35 arid 36 are provided at their ends facing the centerltube part 34 with bent-off flanges 39 and 40. The bentoff flanges 39 and 40 form fastening tabs. The fastening tab 39 has opposite it afastening shoulder 41 at the center tube part 34, and the fastening tab 40 has opposite it afurther fastening shoulder 42 at the center section 34. Between the fastening tab 39 and the fastening shoulder 41 there is arranged a connecting element 43 of metal, which is connected to a fastening projection 44 at the metal enclosure 30. The fastening tab 39, the connecting element 43 and the fastening projection 41 are clamped together by threaded bolts 45 with nuts. In a similar manner, a support element 46 of insulating material is connected by threaded bolts 47 and nuts with the further fastening shoulder 42 and the fastening tab 40. In this manner, the metal tube 33 is not only held in the metal encapsulation 30, but at the same time the outer parts 35 and 36 are connected with the center tube part 34 of the metal tube 33. The metal tube 33, which is grounded through the connecting element 43, then forms an equipotential surface.

At the outside surface of the metal tube 33, iron cores 48 and 49, each with a secondary winding system 50 and 51, are arranged. The iron cores 48 and 49 are provided with pressure pieces 51, 53 and 54, which transmit pressure forces caused by a bracing device 55 onto the fastening shoulders 41 and 42. By means of the bracing device 55, which may consist, for instance, of clamping means in the form of pressure screws, the iron cores 48 and 49 are braced between the fastenin shoulders 41 and 42 and are thereby held on the metal tube 33.

Through the invention, a single-conductor transformer for gas-insulated or liquid-insulated high-voltage installations is proposed, which is held on a metal tube within a high-voltage installation without enclosure of the cores equipped with a secondary system mounted thereon. i1

What is claimed is:

1. A single-conductor transformer for installation and use in a fluid-insulated, high-voltage installation comprising a metal enclosure, a grounded metal shielding tube member having rounded end-faces and being disposed inside the metal enclosure; first mounting means disposed at one end of said tube member attaching the same to the metal enclosure, said first mounting means comprising a first fastening shoulder coupled to and extending from said tube member at said one end thereof, and a fastening projection coupled to and extending from the inner wall of the metal enclosure, said fastening shoulder being connected to'said fastening projection; second mounting means disposed at the other end of said tube member in engagement with 'said inner wall of said enclosure supporting said tube member with respect to the metal enclosure, said' second mounting means'comprising a second fastening shoulder coupled to and extending from said tube member at said other end thereof, and a support element disposed in engagement with the inner wall of said enclosure, said second fastening shoulder being connected to said support element supporting said tube member within said enclosure; at least one transformer core unit including an iron core, and a secondary winding system mounted on said iron core; and third mounting means mounting said transformer core unit on said tube member whereby said tube member supports said transformer core unit within the metal enclosure.

2. The single-conductor transformer of claim 1 wherein the metal enclosure is cylindrical and wherein said tube member is cylindrical.

3. The single-conductor transformer of claim 2, said third mounting means comprising a holding element 7 mounted on said iron core of said transformer core unit for securing said transformer core unit to said tube member.

4. The single-conductor transformer of claim 3 wherein said holding element is made of metal, said holding element being welded to said tube member.

5. The single-conductor transformer of claim 1, said third mounting means comprising clamping means for clamping said iron core of said transformer core unit between said fastening shoulders of said first and second mounting means respectively.

6. the single-conductor transformer of claim 5, said clamping means comprising a plurality of pressure screws.

7. The single-conductor transformer of claim 2 wherein said metal tube comprises a first tubular part having a rounded end-face, and a second tubular part having a rounded end-face and being connected to said first tubular part.

8. The single-conductor transformer of claim 2, said tube member comprising a center tube part and two outer parts connected to respective ends of said center tube part, each of said outer parts having a rounded end-face facing away from said center tube part.

9. The single-conductor transformer of claim 2 wherein said shielding tube member has a longitudinal axis and has rounded end-face portions rounded so as to extend away from said longitudinal axis, said transformer core unit being mounted at the outer wall of said tube member between said rounded end-face portions.

10. The single-conductor transformer of claim 8 wherein one of said outer parts adjoins said center tube part at one end thereof and the other one of said outer parts adjoins said center tube part at the other end 6 tening shoulder extends from said center tube part at said other end thereof, and a second fastening tab is coupled to and extends from said other one of said outer parts, said second fastening shoulder and said second fastening tab both being tightly connected to said support element. 

1. A single-conductor transformer for installation and use in a fluid-insulated, high-voltage installation comprising a metal enclosure, a grounded metal shielding tube member having rounded end-faces and being disposed inside the metal enclosure; first mountIng means disposed at one end of said tube member attaching the same to the metal enclosure, said first mounting means comprising a first fastening shoulder coupled to and extending from said tube member at said one end thereof, and a fastening projection coupled to and extending from the inner wall of the metal enclosure, said fastening shoulder being connected to said fastening projection; second mounting means disposed at the other end of said tube member in engagement with said inner wall of said enclosure supporting said tube member with respect to the metal enclosure, said second mounting means comprising a second fastening shoulder coupled to and extending from said tube member at said other end thereof, and a support element disposed in engagement with the inner wall of said enclosure, said second fastening shoulder being connected to said support element supporting said tube member within said enclosure; at least one transformer core unit including an iron core, and a secondary winding system mounted on said iron core; and third mounting means mounting said transformer core unit on said tube member whereby said tube member supports said transformer core unit within the metal enclosure.
 2. The single-conductor transformer of claim 1 wherein the metal enclosure is cylindrical and wherein said tube member is cylindrical.
 3. The single-conductor transformer of claim 2, said third mounting means comprising a holding element mounted on said iron core of said transformer core unit for securing said transformer core unit to said tube member.
 4. The single-conductor transformer of claim 3 wherein said holding element is made of metal, said holding element being welded to said tube member.
 5. The single-conductor transformer of claim 1, said third mounting means comprising clamping means for clamping said iron core of said transformer core unit between said fastening shoulders of said first and second mounting means respectively.
 6. the single-conductor transformer of claim 5, said clamping means comprising a plurality of pressure screws.
 7. The single-conductor transformer of claim 2 wherein said metal tube comprises a first tubular part having a rounded end-face, and a second tubular part having a rounded end-face and being connected to said first tubular part.
 8. The single-conductor transformer of claim 2, said tube member comprising a center tube part and two outer parts connected to respective ends of said center tube part, each of said outer parts having a rounded end-face facing away from said center tube part.
 9. The single-conductor transformer of claim 2 wherein said shielding tube member has a longitudinal axis and has rounded end-face portions rounded so as to extend away from said longitudinal axis, said transformer core unit being mounted at the outer wall of said tube member between said rounded end-face portions.
 10. The single-conductor transformer of claim 8 wherein one of said outer parts adjoins said center tube part at one end thereof and the other one of said outer parts adjoins said center tube part at the other end thereof; wherein said first fastening shoulder extends from said center tube part at said one end thereof, a first fastening tab is coupled to and extends from said one outer part, and a connecting element is attached to said fastening projection, said first fastening shoulder and said fastening tab both being tightly connected to said connecting element; and wherein said second fastening shoulder extends from said center tube part at said other end thereof, and a second fastening tab is coupled to and extends from said other one of said outer parts, said second fastening shoulder and said second fastening tab both being tightly connected to said support element. 